High Voltage Regulator mounting

[jhaible]

Hi,

I want to build a stabilized power supply for tube circuits, using a 2SK2605 MOSFET.
( http://www.semicon.toshiba.co.jp/docs/datasheet/en/Transistor/2SK2605_en_datasheet_040706.pdf )

It comes in a TO-220NIS package which is supposed to be insulating.

Question is, is it safe to mount this directly to the back of a (earth-grounded) aluminium enclosure, with no extra insulation, when the transistor carries something like 500V DC ?

JH.

 

[gyraf]

You should be safe enough - providing that you have connected your chassis (and thus the mosfet heatsink) to 0V

Jakob E.

 

[jhaible]

[quote author="gyraf"]You should be safe enough - providing that you have connected your chassis (and thus the mosfet heatsink) to 0V

Jakob E.[/quote]

Thanks, Jakob.

This raises another question, about the "0V".

Of course the enclosure is at Earth Ground. Now, if my *signal* GND would not be connected to Earth GND, failure of the FET's insulation would cause -500V on my signal GND.

Normall, I have Signal GND and Earth GND separate, and bridged with 100nF // 100Ohm, to avoid ground Loops ...

JH.

 

[Michael Tibes]

Maybe add 2 diodes antiparallel to the resistor/cap?

Michael

 

[jhaible]

[quote author="Michael Tibes"]Maybe add 2 diodes antiparallel to the resistor/cap?

Michael[/quote]

Yes. Breaks the GND loop, but keeps voltage in failure case low.

JH.